Generally, a digital clock of leaf type comprises a first bobbin supporting sixty leaf-like display members each carrying a numeral from "00" to "59", and a second bobbin supporting twenty-four leak-like display members each carrying a numeral from "1" to "24". The first and the second bobbin are mounted on a common shaft, journaled for rotation on a frame, so as to be rotatable relative to each other, and the first bobbin is driven to rotate at a rate of one revolution per hour by a motor having a uniform speed. The rotation of the first bobbin is transmitted through a suitable speed reduction transmission to the second bobbin so that the second bobbin rotates 1/24 revolution per that of the first bobbin. As the first bobbin rotates, the minute's display members carried thereon also rotate presenting a different minute's display member for view for each minute. A shift of the hour display members takes place in synchronism with the change of the minute's display from "59" to "00".
A conventional rotary transmission used in the usual digital clocks of the type mentioned above to provide a coupling between the both bobbins comprises an intermediate shaft disposed laterally of the time display mechanism in parallel relationship with the main shaft. The intermediate shaft carries a speed reduction gear which is loosely fitted thereon and which meshes with a gear substantially integral with the first bobbin and another gear substantially integral with the second bobbin. The provision of an increased number of gears result in a troublesome assembly operation. The location of the rotary transmission toward one end of the clock is unfavorable to the design of the clock. Finally, the location of the minute's display and the hour's display close to each other is undesirable in providing a clearly visible indication of the time.